Spinel compounds

The anion lattice in the spinel structure (space group ) is composed of a cubic close-packed network of oxygen atoms as in the case of layered compounds. Transition metal cations are located in the octahedral and Li+-Ions in the tetrahedral sites, whereas diffusion of Li+-Ions occurs along with the three-dimensional (3D) interstitial space in the M2O4 spinel framework.

Despite having a theoretical specific capacity of only 148 mAh g−1, LiMn2O4 (LMO) is regarded as a suitable cathode material to replace LCO due to its intrinsic lower cost. However, the material was found to encounter severe capacity fading due to manganese dissolution, Jahn-Teller distortion and the development of micro-strains. Cationic substitution with other elements, such as Ni, has been used to stabilize the structure and led to the development of the HV spinel LiNi0.5Mn1.5O4 (LNMO). Due to its high operation potential (4.7 V vs. Li/Li+) and theoretical specific capacity of 147 mAh g−1, LNMO has emerged as an attractive HV cathode material.